The present invention generally relates to compositions for dyeing keratin fibers. More specifically, the present invention is directed to compositions for dyeing keratin fibers, such as hair, which employ alkyl ketal esters as solvents or co-solvents.
A large number of formulated products for dyeing hair are produced and sold. Because these products differ enormously, as do the conditions under which they are used, the individual products tend to be formulated specifically for the end-use application for which they are intended.
Formulators of products for dyeing keratin fibers, such as hair dyeing products, often find themselves simultaneously addressing many product needs which are often competing and sometimes even contradictory. For example, many hair dyeing formulations contain an active (such as a hair dye), which lends particular functional attributes to the product. In many cases, it is desirable to increase the concentration of the active, or to produce a product that contains the active in a specific type of product form (such as a solution, lotion, cream, gel, etc.), but the formulator is limited by the solubility of the active in the other ingredients in the product. There are several approaches to dealing with this problem, including the use of various types of emulsifiers, oils, cosolvents, and the like, but it is quite often the case that other requirements, such as the form of the product, are incompatible with the presence of such materials in large quantities. These product form concerns may be imposed by the way in which the particular product is to be applied and used; in other cases, these may be due to consumer preferences and/or expectations. Sometimes both factors are at play.
In other cases, the presence or absence of specific materials is important. In this regard there is a desire to reduce or even eliminate the presence of volatile organic compounds from hair dyeing formulations, in favor of alternative solvents. Some formulatory ingredients, such as ethanol, can dry the skin and in some cases are to be avoided for that reason, or for other reasons, such as VOC regulations in some jurisdictions or flammability concerns. Conversely, there are other cases in which ethanol and/or another relatively volatile material is wanted, so the product dries rapidly when it is applied, for example. Nonetheless, it remains necessary to include the active, and it is often desirable to provide the active in a high concentration.
In many cases, the addition of emulsifiers, oils, cosolvents and like materials can cause the product to spread poorly, or feel greasy or heavy. This concern exists even in general purpose products that contain no actives, but concerns exist in active-containing products as well. It would be desirable in some cases to provide hair dyeing compositions which have good spreading characteristics, a non-greasy feel and/or a less heavy feel. Moreover, the use of materials based on renewable resources is becoming of increasing interest as formulators redesign their products to meet environmental sensitivities of their consumer bases.
Yet, another consideration is the compatibility amongst the various ingredients, because many hair dyeing formulations contain both hydrophilic and hydrophobic components. These ingredients tend not to mix into each other. In order to create a product which does not rapidly separate into oil-rich and water-rich layers, it is often necessary to include a number of emulsifiers, cosolvents, or thickeners into the product, so it becomes kinematically stable. These emulsifiers, cosolvents, and thickeners often play little role in the function or performance of the product (i.e., are not “actives”), although they can affect the spreading characteristics and feel on the skin and in the hair. They mainly are present to permit the various functional ingredients to coexist in a stable product form or to provide a desired feel or consistency to the product. The need to include these can lead to a lot of complexity in the formulations, and/or the inclusion of ingredients (such as volatile or drying organic solvents, for example) which would more preferably be omitted. In addition, the formulations tend to be very sensitive to small compositional changes. Small changes to a formulation often destabilize it, requiring a new balance of ingredients.